1. Field of the Invention
The present invention relates to a seat reclining mechanism.
2. Description of the Related Art
Heretofore, there has been known a seat reclining mechanism designed to be mounted to a seat cushion and a seat back so as to allow the seat back to be reclined. JP 2001-017259A and JP 2004-154585A disclose a reclining mechanism which comprises a guide bracket adapted to be mounted to either one of a seat cushion and a seat back, an internal gear member (i.e., internally-toothed gear member) adapted to be mounted to a remaining one of the seat cushion and the seat back, a plurality of lock gear members disposed between the guide bracket and the internal gear member and adapted to be slidingly guided in a radial direction, a rotatable cam adapted to move the lock gear members in both a lock direction causing the lock gear members to be brought into engagement with the internal gear member and an unlock direction causing the lock gear members to be released from the engagement with the internal gear member, and a lock spring biasing the rotatable cam in a lock-causing rotation direction.
In this mechanism, when an operator operates an operation lever to rotate the rotatable cam in a direction opposite to the lock-causing rotation direction, the lock gear members are moved in the unlock direction through a circular lever (actuating plate), and released from the engagement with the internal gear member. Thus, the seat back can be forwardly or rearwardly inclined. Then, when the operator releases his/her hand from the operation lever, the rotatable cam is rotated in the lock-causing rotation direction by a biasing force of the lock spring, and the lock gear members are moved in the lock direction and brought into engagement with the internal gear member. Thus, the seat back is locked at an intended inclined position.
In the above mechanism, if a center of the rotatable cam is displaced from a normal position due to the biasing force of the lock spring, the lock gear members are likely to become unable to be evenly moved, which leads to instability in lock function of the lock gear members.
For this reason, the rotatable cam is integrated with an operation member, such as an operation rod connected to the operation lever, and the operation member supported by a bearing member, such as a knuckle bracket, provided outside the reclining mechanism, so as to perform centering of the rotatable cam.
However, in the structure designed to support the operation member by the bearing member, such as a knuckle bracket, the operation member and the bearing member have to be prepared with a high degree of dimensional accuracy to cause a problem about an increase in cost.